Effects of raw and hydrolysed Nannochloropsis gaditana biomass included at low level in finishing diets for gilthead seabream (Sparus aurata) on fillet quality and shelf life

Abstract

Numerous studies evaluating the effects of the incorporation of microalgae in feeds have reported favourable impacts on different physiological aspects of aquacultured fish. Although productivity is the major goal in terms of profitability in fish farming, qualitative aspects are gaining the attention of producers, given the relevance of quality attributes related to organoleptic parameters, proximal composition, and shelf life on the commercial value of fish. Indeed, microalgae are acknowledged for their richness in substances with potential positive effects on all those quality attributes. In this context, this study assesses the effects of finishing diets enriched with the microalga Nannochloropsis gaditana, either crude or enzymatically hydrolysed, on several quality parameters of gilthead seabream (Sparus aurata) fillets. Two inclusion levels (2.5 and 5%) of raw and enzymatically hydrolysed microalgal biomass were incorporated into diets, plus a microalgae-free control diet, and a 42-day feeding trial was carried out on fish of commercial size (approx. 500 g body weight). The influence of the experimental diets on fish biometry, fillet quality parameters, and shelf life was evaluated. The results indicate, overall, that microalgae-enriched diets yielded favourable, dose-dependent effects on several objective quality parameters of fillets, namely, improved fatty acid profile, reduced microbial counts, enhanced lipid oxidative status, and improved textural and skin colour attributes. Although the enzymatic pre-treatment of the microalgal biomass was expected to impact positively its functional effects on all quality parameters, however, no general trend was observed.